Stainless steel weld clad cylinder interconnected by a groove and gap also weld covered by stainless steel

ABSTRACT

The invention broadly comprises forming a weld preparation groove in the surface of a cylindrical roller, said groove being parallel to the longtitudinal axis of the roller. The groove is filled with a weld material. Subsequently, the outer surface of the cylinder is welded with a compatible welding material to coat the cylinder surface. The weld materials both for the groove and the surface are compatible such that when the surface is welded, the weld material in the groove is recast to form a homogeneous grain structure with the surface weld. The slot is then formed and the surfaces of the facing walls of the slot, the slot edges and the roller surface are uniformly coated.

BACKGROUND AND BRIEF SUMMARY OF THE INVENTION

High speed web type printing presses consist of two side frames whichare bolted together by spacer pieces. The frames carry several highperipheral speed cylindrical rollers, some of which hold a master printform. These master print forms are coated with various colors of ink.The inks are typically solvent based and are mildly corrosive to theface of the rollers. Most of the rollers used are non stainless steel.Their diameters are from 4 to 16 inches and they may be up to 96 inchesin length.

Each roller contains a cut deep channel or slot which is parallel to thelongitudinal axis of the roller. Into this slot is inserted a "locking"device which positions and firmly fastens the master print form to thehigh speed turning roller. The outer surface of the roller is coatedwith a hard chrome surface which prevents chemical corrosion of thecylinder body. In addition the opposed walls of the slot are alsochromed a fixed distance from the outer surface of the roller inwardly.It is extremely difficult to plate the walls of the slot andparticularly the edges defined by the roller surface and the walls ofthe slot. It has been found that these edges and wall surfaces typicallyhave pin holes and/or blisters. The solvents in the inks permeatethrough the pin holes and/or blisters and corrode the underlyingsurface. The corrosion results in the discoloration or streaking of themaster print forms. When this corrosion conditions exists, the cylindersmust be replaced or reconditioned.

One solution would be the use of solid stainless forgings for therollers but the cost is prohibitive. Another possible solution isstainless coatings of the surface of the cylinder and a stainlessoverlay of the slot opening. However, this practice is "blocked"metallurgically because the two interfaces are not metallurgically boundtogether such that they have a contiguous grain structure. Internalstresses at the grain boundaries of the respective welds developallowing the solvents to permeate through, corroding the underlyingsurface.

The invention described herein is a method for coating cylindricalrollers that carry master print forms and the rollers produced by theprocess. A welded interface between a stainless covered roller surfaceand a weld overlay of the slot opening results in a homogenious mixtureof stainless welding free from internal stresses and produces acontinuous uniform grain structure. The invention provides both asurface free of pin holes and bubbles and eliminates the need for thechrome plating of rollers.

The invention broadly comprises forming a weld preparation groove in thesurface of a cylindrical roller, said groove being parallel to thelongtitudinal axis of the roller. The groove is filled with a weldmaterial. Subsequently, the outer surface of the cylinder is welded witha compatible welding material to coat the cylinder surface. The weldmaterials both for the groove and the surface are compatible such thatwhen the surface is welded, the weld material in the groove is recast toform a homogeneous grain structure with the surface weld. The slot isthen formed and the surfaces of the facing walls of the slot, the slotedges and the roller surface are uniformly coated.

In a preferred embodiment, the weld material is stainless steel.However, the weld material may be selected from the following materials,which may be used alone or in combination, belonging to the stainlesssteel family and is referred to as the austenitic and martensiticchromium nickel group. As long as the weld material in the groove hasthe characteristic of being able to be recast when the roller surface iscoated by welding and to reform into a grain structure which ishomogeneous with the grain structure of the material used on the surfacethen that material is within the scope of the invention.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a prior art cylinder;

FIG. 2 is a partial end view of FIG. 1;

FIG. 3 is an end view of FIG. 2 chrome plated;

FIG. 4 is an isometric view of FIG. 1 with the prior art defects;

FIG. 5 is an isometric view of a cylinder of the invention showing theunwelded groove and the surface overlay welding;

FIG. 6 is an isometric view of a cylinder of the invention containing alongitudinal weld and surface overlay welding; and

FIG. 7 is an end view of FIG. 6 after the slot has been cut.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 and 2 illustrate a cylindrical roller 10, which would hold amaster print form, comprising a metal body 12 characterized by acylindrical passage 14 and a longtitudinal slot 16 formed in the outerbody surface 18. The slot walls 20 and 22 define with the surface 18,edges 24 and 26.

FIG. 3 is an end view of roller 10 with chrome plating 28 on thecylinder surface 18, the plating also covering the walls 20 and 22 andedges 24 and 26. When chrome plating, say for example with a currentdensity of 6,000 amp per square inch on the surface 18, the currentdensity virtually reaches infinity on the edges 24 and 26. Thus, theedges on these rollers are the `Achillies Heels` of the rollerconcerning the susceptibility to corrosion. It is extremely difficult tobuild up the plating on these edges.

FIG. 4 shows the plated edges with minute pin holes 30, or grape-likechrome beads 32 formed during the chroming process which later breakoff, both leaving corrosive voids.

FIG. 5 shows a roller 40 of the invention having a weld preparationgroove 42 formed therein.

FIG. 6 shows the roller 40 overlaid partially with stainless weldelectrode 46. Also, the groove 42 is filled with stainless weldelectrode 44.

When the weld electrode overlay 46 passes over the weld electrode 44, aremelt casting process takes place at the interface between the weldsthus forming a uniform metallurgical bond and grain structure resultingin an area 48 of homogeneous metal crystal grain structure. In practice,the overlay extends from one end of the roller 40 to the other.

FIG. 7 shows the cylinder 40 with a slot opening 50 cut through thesolid stainless longitudinal weld 44 to the outer face of weld 46. Alsoformed is a cylindrical passage 52. The opposed `edges` 54 and 56 of thecylinder of the invention are concave surfaces. Comparing the edges 24and 26, FIG. 3, with the edges 54 and 56 illustrates graphically how theprior art problem is overcome, namely, the coating on the `edges` isrelatively thick.

The method of making the cylinder of my invention will further beexplained with reference to the following, non-limiting example.

The thickness of the welds 58 and 60 are greater than the weld thicknesson the surface.

Referring to FIG. 6, a cylinder 40, say for example 12 inches indiameter and 80 inches in length, has a groove 42 formed therein, thegroove having the dimensions of approximately 1 to 2" wide and 1/2"deep. The groove is filled with the stainless weld electrode 44 by usingvarious welding processes such as shielded metal arc, submerged arcwelding, gas metal arc, gas tungsten arc, plasma arc and other weldingtechniques such as pulsating arc.

The entire surface is overlaid with stainless weld electrode 46 by usingsimilar processes as described previously. Subsequently, the slot 50 andcylindrical passageway 52 are formed in the cylinder by machiningtechniques including mill cutting, single point tool cutters, broachingother close tolerance methods.

These techniques are well known in the art and need not be described indetail.

Having described my invention, what I now claim is:
 1. A method forcoating a print cylinder which includes:forming a weld preparationgroove in the surface of the cylinder; filling said groove with weldmaterial; welding onto said surface a weld material metallurgicallycompatible with the weld material in the groove; recasting the weldmaterial in the groove when the weld material is welded on the surfaceto form a homogeneous metal grain structure therebetween; and forming aslot in the cylinder through the groove and the cylinder surface, theslot having opposed edges, the edges extending from the surface inwardlythrough the groove, with reference to the longtitudinal axis of thecylinder.
 2. The method of claim 1 which includes:forming a weldpreparation groove having a concave surface.
 3. The method of claim 2which includes:forming a slot in the cylinder which extends beyond theconcave surface of the groove.
 4. The method of claim 1 wherein the weldmaterials are stainless steel.